US9157769B2 - Reference signal generation apparatus and reference signal generation system - Google Patents

Reference signal generation apparatus and reference signal generation system Download PDF

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US9157769B2
US9157769B2 US14/270,721 US201414270721A US9157769B2 US 9157769 B2 US9157769 B2 US 9157769B2 US 201414270721 A US201414270721 A US 201414270721A US 9157769 B2 US9157769 B2 US 9157769B2
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signal
light
point detection
reference point
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US20140339404A1 (en
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Akihide Kimura
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Mitutoyo Corp
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
    • G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
    • G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
    • G01D5/347—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells using displacement encoding scales
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
    • G01D5/244—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing characteristics of pulses or pulse trains; generating pulses or pulse trains
    • G01D5/24428—Error prevention
    • G01D5/24433—Error prevention by mechanical means
    • G01D5/24438—Special design of the sensing element or scale
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
    • G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
    • G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
    • G01D5/36—Forming the light into pulses
    • G01D5/366—Particular pulse shapes
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
    • G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
    • G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
    • G01D5/36—Forming the light into pulses
    • G01D5/38—Forming the light into pulses by diffraction gratings

Definitions

  • the present invention relates to a reference signal generation apparatus and a reference signal generation system.
  • Optical encoders are widely used to detect a position of a measurement device and the like.
  • a scale for detecting a relative position and a scale for detecting a reference position are provided.
  • the incremental encoder reads the scale for detecting a reference position so as to convert detected relative position information into absolute position information. Therefore, the incremental encoder is required to detect a reference position with high accuracy.
  • Japanese Unexamined Patent Application Publication No. 10-332431 a reference signal is generated based on one edge of the reference point detection pattern that has been read. Therefore, the edge to be a base changes according to the reading direction, and thus the timing of the reference signal changes. Accordingly, this method is unfavorable in principle in terms of improving the accuracy of a reference signal.
  • Japanese Patent Translation Publication No. 2009-515182 can correct the position of a reference signal, it is necessary to perform a correction operation in advance. This will become a constraint in an operation of an encoder.
  • Japanese Unexamined Patent Application Publication No. 2000-304574 can expect to generate a highly accurate reference signal, as the light-receiving elements receive light from the plurality of respective reference point detection patterns, an optical system and the like is required. Therefore, components unnecessary in a normal encoder are added, making the configuration complicated. Further, when the reference point detection pattern is miniaturized to improve accuracy of a reference signal, a diffraction effect will become stronger and it is thus difficult to effectively read the reference point detection pattern.
  • the present invention is made in light of the above circumstances, and an object of the present invention is to generate a highly accurate reference signal with a simple configuration.
  • a first exemplary aspect of the present invention is a reference signal generation apparatus that includes: a reference point detection light-receiving unit that receives light from a reference point detection pattern, in which the light is emitted from a light source; and a reference signal generation circuit that generates a reference signal from a reading result of the reference point detection pattern read by the reference point detection light-receiving unit.
  • the reference point detection light-receiving unit includes: first to third light-receiving elements that are aligned in order in a first direction, output a reading result of the reference point detection pattern as first to third signals, respectively, and have a first width in the first direction, in which the first direction is a reading direction of the reference point detection pattern; a fourth light-receiving element that is disposed between the first light-receiving element and the second light-receiving element, outputs the reading result of the reference point detection pattern as a fourth signal, and has a second width in the first direction; and a fifth light-receiving element that is disposed between the second light-receiving element and the third light-receiving element, outputs the reading result of the reference point detection pattern as a fifth signal, and has the second width in the first direction.
  • the reference signal generation circuit outputs the reference signal that starts at a period where levels of a sixth signal, which is obtained by adding the first signal and the fourth signal, and a seventh signal, which is obtained by adding the second signal and the fifth signal, become equal, and ends at a period where levels of an eighth signal, which is obtained by adding the fourth signal and the second signal, and a ninth signal, which is obtained by adding the fifth signal and the third signal, become equal.
  • a second exemplary aspect of the present invention is the above-mentioned reference signal generation apparatus, in which the first width is different from the second width.
  • a third exemplary aspect of the present invention is the above-mentioned reference signal generation apparatus, in which the first width is smaller than the second width.
  • a fourth exemplary aspect of the present invention is the above-mentioned reference signal generation apparatus, in which, in the reference signal generation circuit, the reference signal starts at a period where a value obtained by subtracting the seventh signal from the sixth signal becomes a predetermined value, and the reference signal ends at a period where a value obtained by subtracting the ninth signal from the eighth signal becomes a predetermined value.
  • a fifth exemplary aspect of the present invention is the above-mentioned reference signal generation apparatus, in which the reference signal generation circuit generates a first comparison signal indicating a result of a comparison between the signal obtained by subtracting the seventh signal from the sixth signal and a first fixed potential that indicates the predetermined value, generates a second comparison signal indicating a result of a comparison between the signal obtained by subtracting the ninth signal from the eighth signal and the first fixed potential, and outputs a signal indicating a logical AND between the first comparison signal and the second comparison signal as the reference signal.
  • the reference signal generation circuit generates a first comparison signal indicating a result of a comparison between the signal obtained by subtracting the seventh signal from the sixth signal and a first fixed potential that indicates the predetermined value, generates a second comparison signal indicating a result of a comparison between the signal obtained by subtracting the ninth signal from the eighth signal and the first fixed potential, and outputs a signal indicating a logical AND between the first comparison signal and the second comparison signal as the reference signal.
  • a sixth exemplary aspect of the present invention is the above-mentioned reference signal generation apparatus, in which the reference signal generation circuit includes: a first adder that outputs the sixth signal that is obtained by adding the first signal and the fourth signal; a second adder that outputs the seventh signal that is obtained by adding the second signal and the fifth signal; a third adder that outputs the eighth signal that is obtained by adding the fourth signal and the second signal; a fourth adder that outputs the ninth signal that is obtained by adding the fifth signal and the third signal; a first subtracter that outputs a first difference signal that is obtained by subtracting the seventh signal from the sixth signal; a second subtracter that outputs a second difference signal that is obtained by subtracting the ninth signal from the eighth signal; a first comparator that outputs the first comparison signal that is a result of a comparison between the first difference signal and the first fixed potential; a second comparator that outputs the second comparison signal that is a result of a comparison between the second difference signal and the first fixed potential; and a first AND circuit that outputs
  • a seventh exemplary aspect of the present invention is the above-mentioned reference signal generation apparatus, in which the reference signal generation circuit further includes: a third subtracter that outputs a third difference signal that is obtained by subtracting the first fixed value from an added value of the first to fifth signals; a third comparator that outputs a third comparison signal that is a result of a comparison between the third difference signal and a second fixed potential; and a second AND circuit that outputs a logical AND between the logical AND, which is between the first comparison signal and the second comparison signal, and the third comparison signal as the reference signal.
  • the reference signal generation circuit further includes: a third subtracter that outputs a third difference signal that is obtained by subtracting the first fixed value from an added value of the first to fifth signals; a third comparator that outputs a third comparison signal that is a result of a comparison between the third difference signal and a second fixed potential; and a second AND circuit that outputs a logical AND between the logical AND, which is between the first comparison signal and the second comparison signal,
  • a eighth exemplary aspect of the present invention is the above-mentioned reference signal generation apparatus further comprising: a plurality of the reference point detection light-receiving units aligned in the first direction corresponding to a plurality of the respective reference point detection patterns aligned in the first direction.
  • the first to fifth signals are output from the plurality of the respective reference point detection light-receiving units to the reference signal generation circuit.
  • An ninth exemplary aspect of the present invention is a reference signal generation system that includes: a light source; a scale including a reference point detection pattern formed thereon that is illuminated by the light source; a reference point detection light-receiving unit that receives light from the reference point detection pattern, in which the light is emitted by the illumination; and a reference signal generation circuit that generates a reference signal from a reading result of the reference point detection pattern read by the reference point detection light-receiving unit.
  • the reference point detection light-receiving unit includes: first to third light-receiving elements that are aligned in order in a first direction, output a reading result of the reference point detection pattern as first to third signals, respectively, and have a first width in the first direction, in which the first direction is a reading direction of the reference point detection pattern; a fourth light-receiving element that is disposed between the first light-receiving element and the second light-receiving element, outputs the reading result of the reference point detection pattern as a fourth signal, and has a second width in the first direction; and a fifth light-receiving element that is disposed between the second light-receiving element and the third light-receiving element, outputs the reading result of the reference point detection pattern as a fifth signal, and has the second width in the first direction.
  • the reference signal generation circuit outputs the reference signal that starts at a period where levels of a sixth signal, which is obtained by adding the first signal and the fourth signal, and a seventh signal, which is obtained by adding the second signal and the fifth signal, become equal, and ends at a period where levels of an eighth signal, which is obtained by adding the fourth signal and the second signal, and a ninth signal, which is obtained by adding the fifth signal and the third signal, become equal.
  • a sixth signal which is obtained by adding the first signal and the fourth signal
  • a seventh signal which is obtained by adding the second signal and the fifth signal
  • a ninth signal which is obtained by adding the fifth signal and the third signal
  • FIG. 1 is a perspective diagram schematically showing a configuration of an encoder 1000 , which is an example of an encoder incorporating a reference signal generation apparatus 100 according to a first exemplary embodiment;
  • FIG. 2 is a top view schematically showing a configuration of a reference point detection light-receiving unit 11 ;
  • FIG. 3 is a circuit block diagram schematically showing a configuration of a reference signal generation circuit 20 ;
  • FIG. 4 is a timing chart showing an operation of the reference signal generation apparatus 100 ;
  • FIG. 5 is a perspective diagram schematically showing a configuration of an encoder 2000 , which is an example of an encoder incorporating a reference signal generation apparatus 200 according to a second exemplary embodiment;
  • FIG. 6 is a top view schematically showing an arrangement of reference point detection light-receiving units 11 a to 11 c according to the second exemplary embodiment
  • FIG. 7 is a top view showing a state where a foreign object is attached to a part of the reference point detection light-receiving unit 11 according to the first exemplary embodiment
  • FIG. 8 is a timing chart showing a signal when a foreign object is attached to a part of the reference point detection light-receiving unit 11 according to the first exemplary embodiment.
  • FIG. 9 is a top view showing a state where a foreign object is attached to a part of a reference point detection light-receiving unit 11 a according to the second exemplary embodiment.
  • a reference signal generation apparatus 100 is used to determine a reference position of an incremental encoder that is used to determine a position of a measurement device and the like.
  • an example of an encoder incorporating the reference signal generation apparatus 100 shall be explained first. Note that as the encoder explained below incorporates a reference signal generation apparatus that generates a reference signal, the encoder may be understood as one aspect of a reference signal generation system in a broad sense.
  • FIG. 1 is a perspective diagram schematically showing a configuration of an encoder 1000 , which is an example of an encoder incorporating the reference signal generation apparatus 100 according to the first exemplary embodiment.
  • the encoder 1000 includes the reference signal generation apparatus 100 , a light source 2 , an optical element 3 , an index scale 4 , and a scale 5 .
  • the light source 2 is, for example, an LED (Light Emitting Diode) and emits light on the index scale 4 and the scale 5 .
  • the optical element 3 is, for example, a collimator that converts light 2 a from the light source 2 into parallel light 2 b .
  • the index scale 4 and the scale 5 are arranged in order on an optical axis (a Z direction) of the parallel light 2 b.
  • a reference point detection pattern 4 a and a position detection pattern 4 e are formed on the index scale 4 .
  • the reference point detection pattern 4 a and the position detection pattern 4 e are formed as slits perforated on a plate-like member.
  • a reference point detection pattern 5 a and a position detection pattern 5 e are formed on the scale 5 .
  • the reference point detection pattern 5 a and the position detection pattern 5 e are formed as slits perforated on a plate-like member.
  • the index scale 4 and the scale 5 may be regarded as being an integrated component that is a scale on which the reference point detection pattern is formed.
  • the reference signal generation apparatus 100 is configured as an apparatus to read the reference point detection pattern 5 a that is irradiated by light emitted from the light source 2 and generate a reference signal.
  • a contrast of the reference point detection pattern 5 a is different from surroundings of the reference point detection pattern 5 a by the irradiated light. Accordingly, the reference signal generation apparatus 100 recognizes the reference point detection pattern 5 a as a bright pattern.
  • the reference signal generation apparatus 100 includes a light-receiving unit 1 and a reference signal generation circuit 20 .
  • the light-receiving unit 1 includes a position detection light-receiving unit 1 b and a reference point detection light-receiving unit 11 .
  • the position detection light-receiving unit 1 b reads a pattern of the position detection pattern 5 e that is irradiated by light transmitted through the position detection pattern 4 e .
  • the position detection light-receiving unit 1 b outputs a signal indicating a read result to a position detection unit (not shown in the drawings).
  • the position detection unit (not shown in the drawings) determines a detected position based on the received signal.
  • FIG. 2 is a top view schematically showing a configuration of the reference point detection light-receiving unit 11 according to the first exemplary embodiment.
  • the reference point detection light-receiving unit 11 includes five light-receiving elements PD 11 to PD 15 arranged in an X direction (also referred to as a first direction) that is the reading direction of the reference point detection pattern 5 a .
  • the light-receiving elements PD 11 to PD 15 are aligned in order in the X direction with a gap D therebetween.
  • the width of the light-receiving elements PD 11 , PD 13 , and PD 15 in the X direction is W1
  • the width of the light-receiving elements PD 12 and PD 14 in the X direction is W2 (W2>W1).
  • an arranging pitch of the light-receiving elements PD 11 and PD 13 in the X direction and an arranging pitch of the light-receiving elements PD 12 and PD 14 in the X direction shall be an arranging pitch P.
  • the light-receiving elements PD 11 , PD 13 , and PD 15 shall also be referred to as first to third light-receiving elements, respectively.
  • the light-receiving elements PD 12 and PD 14 are also referred to as fourth and fifth light-receiving elements, respectively.
  • W1, W2, and D are parameters that determine a pulse width of the reference signal that is output from the reference signal generation apparatus 100 .
  • W2>W1 is desirable.
  • the gaps between the light-receiving elements PD 11 to PD 15 were explained as being D, the gaps between the light-receiving elements PD 11 to PD 15 may not be the same.
  • one of W1 and W2 shall be referred to as a first width
  • the other one of W1 and W2 shall be referred to as a second width.
  • the reference point detection pattern 5 a is read in order by the light-receiving elements PD 11 , PD 12 , PD 13 , PD 14 , and PD 15 .
  • the light-receiving elements PD 11 to PD 15 output brightness or darkness of the reference point detection pattern 5 a that has been read as reading signals S 11 to S 15 , respectively, to the reference signal generation circuit 20 .
  • the reading signals S 11 , S 13 , and S 15 are also referred to as first to third signals, respectively.
  • the reading signals S 12 and S 14 are also referred to as fourth and fifth signals, respectively.
  • the X direction is a direction vertical to the Z direction. Further, a direction vertical to the X direction and the Z direction is an Y direction (also referred to as a second direction).
  • FIG. 3 is a circuit block diagram schematically showing a configuration of the reference signal generation circuit 20 .
  • the reference signal generation circuit 20 includes subtracters 21 to 23 , comparators 24 to 26 , AND circuits 27 and 28 , and adders 41 to 44 .
  • the subtracters 21 to 23 shall also be referred to as first to third subtracters, respectively.
  • the comparators 24 to 26 shall also be referred to as first to third comparators, respectively.
  • the AND circuits 27 and 28 shall also be referred to as first and second AND circuits, respectively.
  • the adders 41 to 44 shall also be referred to as first to fourth adders, respectively.
  • the reading signal S 1 which is obtained by adding the reading signals S 11 and S 12 , is input to a non-inverting input, while a ground potential (also referred to a first fixed potential) is supplied to an inverting input terminal.
  • An output terminal of the adder 41 is connected to a non-inverting input terminal of the subtracter 21 . That is, the adder 41 outputs the reading signal S 1 , which is obtained by adding the reading signal S 11 and S 12 , to the non-inverting input terminal of the subtracter 21 .
  • a reading signal S 2 which is obtained by adding the reading signals S 13 and S 14 , is input to a non-inverting input, while a ground potential is supplied to an inverting input terminal.
  • An output terminal of the adder 42 is connected to an inverting input terminal of the subtracter 21 . That is, the adder 42 outputs the reading signal S 2 , which is obtained by adding the reading signals S 13 and S 14 , to the inverting input terminal of the subtracter 21 .
  • a reading signal S 3 which is obtained by adding the reading signals S 12 and S 13 , is input to a non-inverting input, while a ground potential is supplied to an inverting input terminal.
  • An output terminal of the adder 43 is connected to a non-inverting input terminal of the subtracter 22 . That is, the adder 43 outputs the reading signal S 3 , which is obtained by adding the reading signals S 12 and S 13 , to the non-inverting input terminal of the subtracter 22 .
  • a reading signal S 4 which is obtained by adding the reading signals S 14 and S 15 , is input to a non-inverting input terminal, while a ground potential is supplied to an inverting input terminal.
  • An output terminal of the adder 44 is connected to an inverting input terminal of the subtracter 22 . That is, the adder 44 outputs the reading signal S 4 , which is obtained by adding the reading signals S 14 and S 15 , to the inverting input terminal of the subtracter 22 .
  • the subtracter 21 subtracts the reading signal S 2 from the reading signal S 1 and outputs a subtraction result as a difference signal T 1 .
  • the subtracter 22 subtracts the reading signal S 4 from the reading signal S 3 and outputs a subtraction result as a difference signal T 2 .
  • the subtracter 23 As for the subtracter 23 , the reading signals S 11 to S 15 are input to the non-inverting input, while the ground potential is supplied to an inverting input terminal. The subtracter 23 subtracts the ground potential from the added signal of the reading signals S 11 to S 15 and outputs a subtraction result as a difference signal T 3 .
  • reading signals S 1 to S 4 are also referred to as sixth to ninth signals, respectively.
  • the ground potential is input to a non-inverting input terminal, and the difference signal T 1 is input to an inverting input terminal.
  • the comparator 24 outputs a result of a comparison between the ground potential and the difference signal T 1 as a signal Z 1 .
  • the comparator 25 the difference signal T 2 is input to a non-inverting input terminal, and the ground potential is input to an inverting input terminal.
  • the comparator 25 outputs a result of a comparison between the difference signal T 2 and the ground potential as a signal Z 2 .
  • the difference signal T 3 is input to a non-inverting input terminal, and a reference potential Vref (also referred to as a second fixed potential) is input to an inverting input terminal.
  • the comparator 26 outputs a result of a comparison between the difference signal T 3 and the reference potential Vref as a signal Z 3 .
  • the signals Z 1 to Z 3 shall also be referred to first to third comparison signals, respectively.
  • the AND circuit 27 outputs a logical AND between the signals Z 1 and Z 2 as a pulse signal Z 4 .
  • the AND circuit 28 outputs a logical AND between the signal Z 3 and the pulse signal Z 4 as a reference pulse signal Z 5 , which is a reference signal.
  • FIG. 4 is a timing chart showing an operation of the reference signal generation apparatus 100 .
  • the light-receiving element PD 11 reads the reference point detection pattern 5 a , and then a reading waveform is generated in the reading signal S 11 .
  • a speed of reading the reference point detection pattern 5 a shall be V.
  • the light-receiving element PD 12 reads the reference point detection pattern 5 a with a delay of [(W1+D)/V] from the light-receiving element PD 11 , and a reading waveform is generated in the reading signal S 12 .
  • the light-receiving element PD 13 reads the reference point detection pattern 5 a with a delay of (P/V) from the light-receiving element PD 11 , and a reading waveform is generated in the reading signal S 13 .
  • a reading waveform is generated in the reading signal S 3 , which is obtained by adding the reading signals S 12 and S 13 .
  • (P/V) ⁇ Tb.
  • a time interval between a peak of the reading signal S 1 and a peak of the reading signal S 3 will be ⁇ Ta if the reading is carried out normally.
  • the light-receiving element PD 14 reads the reference point detection pattern 5 a with a delay of ⁇ Ta from the light-receiving element PD 13 , and a reading waveform is generated in the reading signal S 14 .
  • a reading waveform is generated in the reading signal S 2 , which is obtained by adding the reading signals S 13 and S 14 .
  • a time interval between a peak of the reading signal S 1 and a peak of the reading signal S 2 will be ⁇ Tb if the reading is carried out normally.
  • an intersection point IP 1 is generated in the difference signal T 1 (S 1 -S 2 ).
  • the intersection point IP 1 may be understood as being a point where a level of the reading signal S 1 becomes equal to a level of the reading signal S 2 .
  • the light-receiving element PD 15 reads the reference point detection pattern 5 a with a delay of ⁇ Tb from the light-receiving element PD 13 , and a reading waveform is generated in the reading signal S 15 .
  • a reading waveform is generated in the reading signal S 4 , which is obtained by adding the reading signals S 14 and S 15 .
  • a time interval between a peak of the reading signal S 3 and a peak of the reading signal S 4 will be ⁇ Tb if the reading is carried out normally.
  • an intersection point IP 2 is generated in the difference signal T 2 (S 3 -S 4 ).
  • the intersection point IP 2 may be understood as being a point where a level of the reading signal S 3 becomes equal to a level of the reading signal S 4 .
  • the subtracter 23 outputs the difference signal T 3 , which is a sum signal of the reading signals S 11 to S 15 , as described above.
  • the comparator 24 compares the ground potential with the difference signal T 1 by the above-mentioned configuration. As a result, the signal Z 1 that is output from the comparator 24 becomes HIGH in a period where the difference signal T 1 , which starts at the intersection point IP 1 , is in a period of a negative potential.
  • the comparator 25 compares the signal Z 2 with the ground potential by the above-mentioned configuration. As a result, the signal Z 2 that is output from the comparator 25 becomes HIGH in a period where the difference signal T 2 , which ends at the intersection point 1 P 2 , is in a period of a positive potential.
  • the comparator 26 compares the signal Z 3 with the reference potential. As a result, the signal Z 3 that is output from the comparator 26 becomes HIGH in the period where Z 3 ⁇ Vref.
  • the AND circuit 27 outputs a logical AND between the signal Z 1 and the signal Z 2 as the pulse signal Z 4 . That is, the pulse signal Z 4 is a pulse signal that starts at the intersection point IP 1 and ends at the intersection point IP 2 .
  • the AND circuit 28 outputs a logical AND between the signal Z 3 and the pulse signal Z 4 as the reference pulse signal Z 5 .
  • the pulse signal Z 4 is output as-is, as the reference pulse signal Z 5 .
  • a timing of the reading signal S 3 which is a sum signal of the reading signals S 12 and S 13 , is delayed by ⁇ Ta from the reading signal S 1 , which is a sum signal of the reading signals S 11 and S 12 .
  • a timing of the reading signal S 4 which is a sum signal of the reading signals S 14 and S 15 , is delayed by ⁇ Ta from the reading signal S 2 , which is a sum signal of the reading signals S 13 and S 14 . Consequently, a timing of the intersection point IP 2 is delayed by ⁇ Ta from the intersection point IP 1 .
  • the reference pulse signal Z 5 is a pulse signal with a width sandwiched between the intersection point IP 1 and the intersection point IP 2 .
  • the timing of the intersection point IP 1 is determined only by the arrangement of the light-receiving elements PD 11 to PD 14
  • the timing of the intersection point 1 P 2 is determined only by the arrangement of the light-receiving elements PD 12 to PD 15 .
  • a difference in the timings of the intersection points IP 1 and IP 2 is a constant value determined by the width W1 of the light-receiving elements PD 11 , PD 13 , and PD 15 , the width W2 of the light-receiving elements PD 12 and PD 14 , and the gap D between the light-receiving elements.
  • this configuration is capable of maintaining the pulse width of the reference pulse signal Z 5 , which is a reference signal, to be constant.
  • FIG. 5 is a perspective diagram schematically showing a configuration of an encoder 2000 , which is an example of an encoder incorporating the reference signal generation apparatus 200 according to the second exemplary embodiment.
  • the encoder 2000 has the same configuration as that of the encoder 1000 except that the index scale 4 , the scale 5 , and the reference signal generation apparatus 100 in the encoder 1000 are replaced by an index scale 7 , a scale 8 , and the reference signal generation apparatus 200 , respectively.
  • Reference point detection patterns 4 a to 4 c and a position detection pattern 4 e that are aligned in the X direction are formed on the index scale 7 .
  • Reference point detection patterns 4 b and 4 c are similar to the reference point detection pattern 4 a , an explanation of the reference point detection patterns 4 b and 4 c shall be omitted.
  • Reference point detection patterns 5 a to 5 c and a position detection pattern 5 e that are aligned in the X direction are formed on the scale 8 .
  • the reference point detection patterns 5 a to 5 c are formed at the positions corresponding to the reference point detection patterns 4 a to 4 c , respectively.
  • an explanation of the reference point detection patterns 5 b and 5 c shall be omitted.
  • the reference signal generation apparatus 200 includes a light-receiving unit 6 and a reference signal generation circuit 20 .
  • the light-receiving unit 6 includes reference point detection light-receiving units 11 a to 11 c and a position detection light-receiving unit 1 b .
  • the reference point detection light-receiving units 11 a to 11 c are disposed at the positions corresponding to the reference point detection patterns 5 a to 5 c , respectively.
  • FIG. 6 is a top view schematically showing an arrangement of the reference point detection light-receiving units 11 a to 11 c according to the second exemplary embodiment.
  • the reference point detection light-receiving units 11 a to 11 c have a configuration similar to that of the reference point detection light-receiving unit 11 according to the first exemplary embodiment.
  • the reference point detection light-receiving units 11 a to 11 d are aligned in the X direction, which is the reading direction.
  • the reference point detection patterns 4 a to 4 c and 5 a to 5 c are arranged to correspond to the reference point detection light-receiving units 11 a to 11 c , respectively.
  • FIG. 7 is a top view showing a state where a foreign object is attached to a part of the reference point detection light-receiving unit 11 according to the first exemplary embodiment.
  • FIG. 8 is a timing chart showing a signal when a foreign object is attached to a part of the reference point detection light-receiving unit 11 according to the first exemplary embodiment.
  • FIG. 9 is a top view showing a state where a foreign object is attached to a part of the reference point detection light-receiving unit 11 a according to the third exemplary embodiment.
  • the reading signal S 11 that is output from the light-receiving element PD 12 of the reference point detection light-receiving units 11 a to 11 c will have a distorted waveform due to an influence that the foreign object 50 is attached to the light-receiving element PD 12 of the reference point detection light-receiving unit 11 a .
  • the distortion appears as a distortion in the waveform of the reading signal S 1 .
  • the position of the intersection point moves.
  • the reading signals S 11 to S 15 that are output from the reference point detection light-receiving units 11 a to 11 c are added. Accordingly, even when foreign objects are attached to a part of the plurality of reference point detection light-receiving units, a signal with a normal waveform is output from the reference point detection light-receiving unit to which no foreign object is attached. As a result, even when a foreign object is attached to the light-receiving element PD 12 of the reference point detection light-receiving unit 11 a , a distortion in the waveform of the reading signal S 1 can be reduced. Consequently, it is possible to prevent the intersection point of the difference signal T 1 from moving.
  • the number of the reference point detection patterns and the reference point detection light-receiving units is three has been explained so far, this is merely an example.
  • the number of the reference point detection patterns and the reference point detection light-receiving units may be any plural number other than three.
  • the present invention is not limited to the above exemplary embodiments, and modifications can be made as appropriate without departing from the scope of the present invention.
  • the above reference signal generation circuit is merely an example. That is, as long as a reference signal similar to the one generated by the above reference signal generation circuit can be generated based on a signal from the reference point detection light-receiving unit, the configuration of the reference signal generation circuit may be changed as appropriate.
  • the light source 2 as being an LED, this is merely an example.
  • the LED may be monochrome or white.
  • a laser diode or other laser devices may be used as the light source.
  • a common broadband light source such as a halogen lamp may be used as the light source.
  • the encoder according to the above exemplary embodiments may be a so-called reflective encoder in which light is reflected by a scale and the reflected light is received by a position detection light-receiving unit.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optical Transform (AREA)
  • Measurement Of Optical Distance (AREA)
  • Length Measuring Devices By Optical Means (AREA)
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CN104236606A (zh) 2014-12-24
EP2803948A3 (en) 2014-12-03
CN104236606B (zh) 2018-05-25
EP2803948B1 (en) 2016-11-16
US20140339404A1 (en) 2014-11-20

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